This invention relates to apparatus for using optical radiation to treat dermatological problems and, more particularly, to heads for such apparatus which heads provide an elongated focus area at a selected depth and/or selected preconditioning, for example heating and/or cooling, of a treatment area.
Lasers, lamps, and other sources of electromagnetic radiation, particularly in the optical wavebands, are being increasingly utilized for various dermatological treatments and, in particular, for the removal of unwanted hair, spider veins, leg veins, other veins or other blood vessels which are visible through the patient""s skin, lesions, port-wine stains, tattoos, and the like. In performing such treatments, it is desirable that the cost for the treatment be kept as low as possible, consistent with achieving desired results, and that risk of injury to the patient be minimized.
Since continuous wave (CW) lasers and other CW radiation sources are typically substantially less expensive than pulsed sources of comparable wavelength and energy, for cost reasons, it would be preferable to use CW sources rather than pulsed sources for such dermatological treatments. However, in order to avoid injury to the patient, the duration of energy application to a given area of the patient""s skin must be controlled, this generally resulting in the more expensive pulsed light sources being used for the various dermatological treatments.
Further, since the only way to get radiation to areas where treatment is desired, which areas are normally in the dermis, is to transmit the radiation to such area through the overlying epidermis, some portion of incident radiation is absorbed in the epidermis creating the potential for damage thereto. This is a particular problem where melanin is being targeted in the dermis, as is for example the case for various hair removal treatments, since there is a substantial concentration of melanin in the lower portion of the epidermis at the dermal/epidermal (DE) junction. Further, the deeper in the dermis that treatment is desired, and/or the larger the element being treated, the more energy must be used, this generally involving the use of a more powerfull laser or other radiation source and/or operating such source for longer time durations. This further increases the potential for epidermal damage.
Some attempts have been made in the past to scan a CW radiation source, such as the laser, over a treatment area, which has been done with the radiation source spaced from the skin in order to facilitate movement of the source. However, techniques currently utilized for protecting the epidermis frequently involve contact cooling of the epidermis and, for certain treatments such as hair removal, performing the treatment with pressure applied to the patient""s skin is also desirable. Irradiation by use of a head in contact with the skin also permits more efficient transfer of energy into the patient""s skin, thereby reducing the size of the source required for a given treatment energy density and, therefore, reducing the cost of such source. This cost could be further reduced if the radiation source is not the only source being utilized to heat the area under treatment.
Another problem in performing laser dermatology treatments, particularly when such treatment is to be performed over an area larger than the optical aperture of the applicator being utilized, is to obtain substantially uniform irradiation over the area so that sufficient radiation is applied to all portions of the area to achieve the desired treatment, while no portion of the area has so much radiation applied thereto as to cause thermal damage to the skin. Such uniform irradiation is very difficult with a pulsed source which typically utilize a circular aperture. Typically, the procedure followed is to irradiate a spot with a given pulse and to then reposition the head to an adjacent spot for irradiation. If the spots do not overlap, there will be portions of the area under treatment which do not receive radiation and, unfortunately, the radiation output is frequently not uniform over the entire optical aperture, being greater near the center, and less at the edges. Therefore, there is generally some overlap between adjacent spots. However, this results in some portions of the area under treatment receiving at least a double dose of radiation, which poses a potential danger of thermal damage in these overlap areas. Substantially uniform irradiation of a treatment area is therefore virtually impossible with a pulsed radiation source utilizing existing techniques.
Another problem which increases the energy required from the radiation source utilized is that, for existing systems, heating of the target to achieve the desired therapeutic effect is accomplished solely by radiation from the radiation source. If the temperature of the target could be increased by some type of preheating of the target volume, the amount of energy required from the radiation source to complete the job would be substantially reduced. However, such preheating must be achieved in a way such that the cost of such preheating is not greater than the savings achieved by reduced requirements on the radiation source.
Similarly, in order to protect the epidermis, many procedures require that the epidermis be cooled, preferably to the DE junction, to at least a selected temperature, for example 10xc2x0 C., 0xc2x0 C., or even slightly lower, before radiation is applied. If contact cooling starts when the head is over the target area, this means that there is some delay, perhaps half a second to a second, between the time the head is applied to the patient""s skin and the time the radiation source is fired. With CW, such a delay once the radiation source is over the target area is difficult to achieve and it is therefore preferable that precooling of the epidermis occur for the target area before the radiation source is thereover. An ideal procedure would be to preheat the skin down to the target depth and then to precool to the DE junction, leaving the target depth preheated. Mechanisms in general, and heads in particular, for achieving such precooling and/or preheating followed by precooling have not heretofore existed.
It is also desirable to be able to focus the optical radiation at substantially the target depth. While heads have heretofore existed which are capable of achieving such a focus on a given spot, faster operation, particularly when operating in CW mode, although also when operating in pulse mode under some circumstances, can be achieved if there is a line focus at the target depth rather than a point focus. Mechanisms for achieving such a line focus have also not heretofore existed.
A need therefore exists for improved apparatus for utilizing optical radiation to treat various dermatological conditions, and in particular, improved heads for use in such apparatus which facilitate preheating and/or precooling of the target area, particularly when operating in CW mode, but also when operating in other modes, and which also facilitate achieving of a line focus for the radiation at a selected target depth for enhanced, and in particular, more rapid treatment.
In accordance with the above, this invention provides various heads for use in apparatus for effecting a selected dermatologic treatment in an area of a patient""s skin. For some embodiments, the head includes a block formed of a material having good thermal transfer properties, a plurality of first optical waveguide elements and a plurality of second optical waveguide elements extending through the block, the first and second optical waveguide elements being angled at first and second angles respectively, which angles are selected so that light passing through the first and second optical waveguide elements converge at a selected depth. The optical waveguide elements have radiation applied thereto which is appropriate for the selected dermatologic treatment. The selected depth is in the area under treatment at which the dermatologic treatment is to occur. For some embodiments, a recess is formed in a surface of the head in contact with the patient""s skin, the recess being at the distal end of the optical waveguide elements, and the selected depth is at a selected location in the recess. For these embodiments, a means is provided for moving skin in the area under treatment into said recess as said recess passes thereover. This means may, for example, include a source of negative pressure connected to the recess. For preferred embodiments, the block also has a skin contacting surface which retroreflects radiation leaving the patient""s skin. A mechanism may also be provided for controlling the temperature of either the entire block or selected portions thereof.
For other embodiments, the head includes an astigmatic lens having an elongated outer surface, one side of said surface contacting the patient""s skin in the area to be treated along an elongated line. A mechanism is provided which delivers light of a wavelength suitable for the dermatologic procedure to the lens on a side thereof other than the side contacting the patient""s skin, the lens focusing light delivered thereto to a selected depth in the patient""s skin. The lens may be a cylindrical lens with a diameter such that light delivered thereto is focused to the selected depth, and may be mounted to be either stationary or rotating as the head is moved over a treatment area. For some embodiments, the lens is treated so as to normally have total internal reflection, the total internal reflection being broken at a surface of the lens in contact with the patient""s skin. To achieve the desired focus, the radius of curvature of the cylindrical lens for some embodiments is less than or equal 10 mm. For some embodiments, the selected depth is that for a portion of a hair follicle responsible at least in part for hair growth, for example, the hair bulge or the hair bulb. The selected depth may, for example, be 1 mm to 5 mm.
The mechanism for delivering light to the lens may deliver light along a line substantially parallel to the elongated line contacting the patient""s skin surface and/or may cause light to be delivered to the lens at a variety of angles. A cooling mechanism may also be available for the patient""s skin before the lens makes contact with the skin and/or while the lens is in such contact, the cooling mechanism for some embodiments, including a mechanism for cooling the lens. For some embodiments, the lens focuses light at said selected depth to an astigmatic focus area having a long dimension substantially parallel to the elongated line of lens contact with the skin. Finally, for some embodiments, the mechanism delivering light to the lens scans along the lens in its elongated direction, the scanning being at a selected rate.
More generally, the invention includes a focusing element having a light receiving region, a light delivery region which is adapted to be in contact with the patient""s skin and a region which focuses light entering at said receiving region, the focus, when such element is in contact with the patient""s skin being to an elongated astigmatic focus area at a selected skin depth. A mechanism is included which delivers light of a wavelength suitable for the dermatologic procedure to the light receiving region. The selected depth for some embodiments is the depth for a portion of a hair follicle responsible at least in part for hair growth, for example the hair bulge and/or hair bulb, and may be approximately 1 mm to 5 mm into the skin. A cooling mechanism for the patient""s skin may also be provided, which mechanism is operated before the element makes contact with the skin and/or while the element is in contact therewith.
In accordance with still another embodiment of the invention, the head includes an optically transparent channel for delivering optical radiation of a wavelength appropriate for effecting the treatment in the area, a head portion of a thermally conductive material mounted relative to the channel so that it moves over each segment to be treated of such area before the channel, and a thermal component which controls the temperature of the head portion, and thus of each skin segment prior to treatment. In particular, the component may cool the portion, and thus each skin segment prior to treatment and/or the component may heat the portion, and thus heat each segment prior to treatment. The head may include a block formed of a material having good heat transfer properties, the block being adapted to move over the area during treatment, the channel being formed through the block and the portion being a portion of the block which is forward of the channel as the block is moved over the area. The head portion forward of the channel may be divided into a first thermally conductive portion which is heated and a second thermally conductive portion which is cooled, which portions are thermally insulated from each other, the first portion heating the patient""s skin to the depth where treatment is to be performed and the second portion then cooling the patient""s epidermis prior to irradiation. The head may also include a portion of a thermally conductive material mounted relative to the channel so that it moves over each segment to be treated of the area after the channel; and a thermal component which cools such rear head portion, and thus each skin segment after treatment.
While for preferred embodiments, preheating of the skin in the treatment area is accomplished in conjunction with the use of CW radiation and movement of the head over the treatment area, this is not a limitation on the invention, and preheating of the treatment area is also advantageous when employed with a pulsed radiation source. For such applications, preheating could be achieved by heating the waveguide or the portion of the head in contact with the segment under treatment prior to treatment to heat the skin down to at least to the depth where treatment is desired to a temperature which temperature is below that at which thermal damage occurs; and to then cool the surface in contact with the epidermis to cool the epidermis before irradiation begins. This results in the area under treatment having an elevated temperature when irradiation begins, thereby reducing the energy required from the radiation source. Alternatively, a low energy radiation source, which can be either the same or different than that used for treatment, can be used to perform the preheating operation.
The foregoing and other objects, features and advantages of the invention will be apparent in the following more particular description of preferred embodiments of the invention as illustrated in the accompanying drawings.